4" Rotary Table conversion.

[Boot]

I bought a 4" rotary table ,but in reallity needed a 6" to mount my small 4 jaw chuck. I made an adapter and extension to accomplish mounting the chuck.
The 3 pieces of steel and Al are bolted and located with plugs in the center of the plates. Now the only thing I have to do to it because of the 4 jaw being universal is to regrind the ID of the the jaws because of a .012 run out in them. I have to cut a couple gears so I want it pretty close. I do have a question on putting a load on the jaws to grind them. Can I get away with using a machined circle of steel on the OD in order to grind the ID? What would be the best proceedure?


[IMG]http://i750.photobucket.com/albums/xx142/Boot-010/DSCF0327.jpg

[macona]

Man, that is a lot hanging off that poor rotary table. Why so thick?

Grinding the jaws may not help in the end with that. The wear could be all in the slides.

I think I would just get a cheap chinese chuck, install that, and be done with it.

[justanengineer]

+1 on what macona said. I would triple check where the slop really is, having been told by others that a particular chuck's jaws were out in the past when in fact it was a backing plate issue.

I think rather than try to mate the chuck to the rotab, what I would do is simply make and mount a small face/fixturing plate to the rotab. Even if it hangs off one side more than the other it makes little difference, and keeping your part closer to the rotab itself will increase the rigidity tremendously.

[WCPenney]

Have a look at this LMS adapter plate to use a 4" chuck on a 4" table. Oddly enough it's not listed under the rotary table adapters, but under lathe chuck adapters. I have no idea what the quality is like, as I don't own one, but I'm in the same pickle with a 4" rotab.

http://www.littlemachineshop.com/products/product_view.php?ProductID=3782&category=-1110836144

[Jim Shaper]

I'm with Jerry on this one - I can't fathom that base is rigid enough to handle that much leverage and not induce a taper.

[macona]

No, look at where he is clamping the piece in the chuck all sorts of daylight. Probably just a worn out chuck.

[Sparky_NY]

No, look at where he is clamping the piece in the chuck all sorts of daylight. Probably just a worn out chuck.

Wow, went back and looked at that pic, there sure is a lot of daylight showing. ALSO, maybe its just me but that sure looks to be a 4 jaw chuck in that pic showing daylight, 2 of the jaws "appear" to be centered on the sides of that stock. Probably just a illusion.

[Rosco-P]

Man, that is a lot hanging off that poor rotary table. Why so thick?

Grinding the jaws may not help in the end with that. The wear could be all in the slides.

I think I would just get a cheap chinese chuck, install that, and be done with it.

IMHO, when that rotary table is in "horizontal mode", seems like a lot of breakout force is going to be applied to the table T slots because of the excessive overhang combined with tool induced forces. Chuck too big, RT too small, clunky backplate/adapter setup.

[John Stevenson]

It's a 4 jaw self centring chuck so it will only hold a perfect square.

Thats why they don't make 4 legged milking stools

[Duffy]

I just finished such a conversion, but went a different way. The table has a 2MT taper center hole, and the chuck is a Skinner 4" 3-jaw with reversible jaws. I machined a backing plate with a 2MT stub taper threaded 3/8"-16 for a retaining bolt. The backing plate has a 5/16"-24 stud mounted to engage in any of the three slots in the table. The stud resists rotation and the retaining bolt opposes uplift. Total "daylight" loss to the mounting is 5/16".
Granted, this unit is in no way "heavy duty," but it is, after all, only a 4" table/chuck assembly. For heavy work I have to revert to an 8" RT, but it REALLY steals daylight form my mill/drill!
Sorry, no pics; still havent figured out photobucket!

[Pherdie]

It would seem to me that in the fabrication of your adapter, you have the great beginning of a tru-set style of adapter. Converting to a tru-set can help those chuck centering issues and at the same time reduce both the mass, loading and possible error from your table (as previously mentioned).

Good luck,

Fred

[Sparky_NY]

It's a 4 jaw self centring chuck so it will only hold a perfect square.

Thats why they don't make 4 legged milking stools

Never seen a 4 jaw self centering chuck before, learned something new. Were they made by Bridgeport?

[gnm109]

Never seen a 4 jaw self centering chuck before, learned something new. Were they made by Bridgeport?

That's a good question. I haven't seen one before, either. I have a 4 jaw 4" and 10" and I only use them when I want to dial an item in as close to zero as possible. A self-centering 4 jaw wouldn't seem to be much use.

Also, with my 4 jaw chucks, with the independent jaws, the jaws are reversible which is quite useful.

.

[Jim Shaper]

Similar to the 6 jaws that are out there - you get more grip with less pressure. It has nothing to do with how you consider a 4 jaw useful, other than you can grab square objects as well.

[gnm109]

Similar to the 6 jaws that are out there - you get more grip with less pressure. It has nothing to do with how you consider a 4 jaw useful, other than you can grab square objects as well.

?.................no one was talking about 6 jaw self-centering chucks.